Hand-held electrical devices such as power tools or personal care devices include electric switch units which assist in controlling the supply of power to the motor or other electrically operable elements of the electrical device.
It is of paramount importance that due to environmental factors, that such switches prevent ingress of foreign particulates, dust and water. This is due to longevity of a switch, which typically may be used for numerous cycles when implemented in such an electrical device. Also and importantly, from an occupational health and safety risk standpoint, it is important that ingress of foreign matter and water be prevented from entering a switch, as the ingress of such matter can cause short circuiting as well as electric shock to an operator. Further, such ingress may cause an insulative effect, and cause non-operability of a switch, rendering a device in which the switch is implemented non-operable.
Within the various electrical standards, there exist requirements of prevention of ingress of foreign objects and water, of varying degrees, and applicable ratings are applied to switches depending upon the level of ingress prevention. For example, standards may include ratings or gradings dependent upon the size of particulates of sizes, dust-proofing, and the pressure of water such as from dripping, spraying, powerful water jets, temporary immersion and long term immersion.
Accordingly, depending upon the physical and environmental application, a switch or switch assembly is required to have the requisite level of particulate, dust and water prevention to ingress rating.
For example, hand operable power tools are often exposed to harsh environments such as construction or work sites, whereby there is inherently a high level of dust and particulate matter, as well as often moisture and water. Further, an operator of e device may have wet hands or gloves with liquid thereon, such as uncured cement or wet paint, which needs to be prevented from entering the switch or switch assembly. Also, a power tool when not used may be laid down in a wet or moist environment or be exposed to the splashing of water.
In other applications such as personal care devices, for example hairdryers, inherently there will exist airborne particulate matter as well as water from the hair of an operator or wet surfaces upon which a hairdryer or other device may be laid to rest. Accordingly, from longevity and safety standpoints, ingress into the switch or switch assembly of particulates, dust and water must be suitably resisted or prevented.
There exist various manners in which a switch may be dust proofed or water proofed according to the prior art, such as an encapsulating membrane covering at least the outer exposed portion of the switch including the actuator. However such membranes, through repetitive use and deformation, may tear or become perforated, and permit ingress of particulates, dust and water, and thus have compromised integrity.
Further, the use of such switches or switch assemblies are often bulky, and their implementation in hand-held electrical devices such as hand operable power tools and hand-held personal care devices is often precluded, due to physical space constraints and aesthetic requirements.
Switches as applicable for use in hand-held electrical devices such as hand operable power tools and hand-held personal care devices must not be easily inadvertently activated or requisite settings or positions easily inadvertently altered, due to safety concerns as well as commercial implications.